JPS6013002A - Continuous sintering furnace - Google Patents

Abstract

PURPOSE:To maintain the carbon potential of the gas in a furnace at a prescribed value by providing a pipe for sampling the gas in the furnace for analysis, a pipe for introducing endothermic type converting furnace gas and a pipe for charging enriched gas in the specified positions in a sintering section and controlling the rate of charging the enriched gas. CONSTITUTION:A pipe for sampling gas in a furnace for analysis is provided between the central position of a sintering section of a sintering furnace and the position spaced from said position by the length equiv. to 10% of the overall length of the sintering section in the longitudinal direction of the furnace. A filter and a carbon potential measuring meter are successively attached to the sampling pipe. At least one pipe for introducing endothermic convering furnace gas as a protective atmosphere is connected in the position spaced from the set position of the sampling pipe by the length equiv. to 10-20% of the length of the sintering part toward the rear part of the furnace and a pipe for charging enriched gas is opened in the position spaced by >=1m from the end of the pipe for introducing the converting furnace gas where the pipe opens into the furnace. The rate of charging the enriched gas is controlled by sampling and analyzing of the gas in the furnace to maintain the carbon potential at a prescribed quantity, by which a uniform sintered body is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the carbon potential (hereinafter referred to as c
, p,? J4 This invention relates to a continuous sintering furnace for powder metallurgy that enables the production of sintered bodies with almost completely uniform metal composition and dimensional changes.

Conventionally, like in batch-type carburizing and quenching furnaces, the atmosphere inside the furnace is sampled, H2O1, that is, the dew point or CO2 temperature is measured, and c and p are determined, and deviations from the preset c and p values are determined. It is already well known to amend this by enriching with a hydrocarbon gas such as propane or butane gas. However, this method is difficult to apply in the case of continuous sintering furnaces for powder metallurgy due to the following reasons.

(1) As shown in Fig. 1, the typical continuous mesh belt type furnace is the one shown in Figure 1. It is difficult to clarify whether the measured values of the sampling gas indicate the c, p, values that determine the metal tJl texture of the glaucoma.Similarly, the farthest position of enrichment gas introduction as shown in Fig. 2 It is also difficult to decide.

(2) The de-rossing part that removes the lubricant (mainly zinc stearate) added during molding of powder metallurgy products is often continuous with the sintered part, so the flow of gas can cause
i De-rotation Some contaminated gas may move inside the furnace. In addition, like zinc stearate, decomposition and vaporization progress in the furnace and may float as Zn vapor. Therefore,
These contaminants (
It is difficult to know which method to use to remove dust such as zinc stearate oxide and carbon.

(3) The sampling tube may become clogged due to the above-mentioned contaminants within 1 to 2 hours after the start of sampling.

(4) Metal vapor may enter the measuring part of the I(,0 amount or CO, amount) measuring device, causing a decrease in the accuracy of the meter or the inability to measure.

(5) Even if enrichment gas is introduced to change the values of c and p in the furnace, it often takes several tens of minutes for the effect to take effect. In particular, in furnaces with a brick-type inner structure, the response time of enriched gas tends to be slow. In this case, it is difficult to determine how to set the measurement time and enrichment time for the in-furnace gas.

The developed FJ)4 solves the problems of the conventional technology described above, and by adjusting the c, p, and values of the furnace atmosphere, it is possible to produce a sintered body with almost completely uniform metal structure and dimensional changes. According to the present invention, a continuous sintering furnace for smoothing is provided. A continuous sintering furnace for powder metallurgy equipped with a sintering section and a cooling section, in which an in-furnace gas sampling tube for analysis is connected to the central position of the sintering section and from the central position to the longitudinal direction of the furnace. At the same time, a filter and a carbon potential measuring meter were installed in sequence at the in-furnace gas sampling pipe, and a carbon potential measuring meter was installed in sequence from the installation position of the in-furnace gas sampling pipe toward the rear of the furnace. The length of the sintered part is 10~
Connect a small endothermic converter air inlet pipe as a protective atmosphere to a position separated by a length equivalent to 20%, and connect the enriched gas charging pipe to the furnace of the cough converter air inlet pipe. It is configured to open at a position 1 m or more away from the inner opening end, and to collect and analyze the gas in the furnace, and to control the amount of enriched gas charged to maintain the carbon potential of the gas in the furnace at a predetermined value. A continuous sintering furnace is obtained.

Next, 5 buttons to explain the present invention in detail First, the furnace is not particularly limited, but a furnace core tube type is preferable because it is less affected by the wall. Of course, a brick type furnace can also be used. Hereinafter, the endothermic shift reactor gas will be referred to as RX gas.

As shown in FIG. 3, the optimum gas sampling position for the sintering furnace of the present invention is the center position of the effective sintering length shown as the sintering section and the effective sintering length from the center position toward the rear of the furnace. Set between the position shifted by 10 times. This position corresponds to the center of the soaking section.

If the setting position is too far forward, it will be susceptible to the influence of gas inflow from the degassed part, leading to large fluctuations in measured values or clogging of the sampling tube. Rx into the furnace
The gas may be introduced from any of the points A, B, and C in FIG. 2, or may be introduced from 1, 2, or 3 points at the same time. However, the position shown in enriched gas qB is optimal, and this position is a position separated from the optimal sampling position by 17 to 20'A of the effective waste length toward the rear of the furnace. Therefore, if the Rx gas introduction position of B is set as the above position and the enriched gas piping is connected to this piping, 1 fl of the reactor air
Stirring of Rx gas and enriched gas is promoted. If the enrichment gas introduction position [B] is shifted further back than this, the reaction rate will be slow because it will be shifted from the soaking section of the sintering furnace and the temperature 1 will be lower. Furthermore, if the front position is shifted, the sampling position IfK will be too close, making it impossible to sufficiently measure the enrichment effect.

It is essential to install an adsorption filter to suck gas from the optimal sampling position determined as above and completely remove metal vapors generated from the lubricant used during molding, such as the Zn vapor mentioned above.

It is not a secret that zinc stearate oxide, carbon particles, and other dust other than fixed metal vapors are completely removed by this adsorption filter and then mechanically collected in sequence by the filter.

C and P of the gas purified by fW in this way are considered to be representative values. Set the dew point and CO6 values corresponding to the required C, P, and Ic in advance, and set the Rx gas to be introduced at an intermediate value between the set values.

Although c and p may fluctuate to a low level due to fluctuations in the air inside the furnace, it is unlikely that they will fluctuate to a high level, so knowing the fluctuations of the dew point 1fc from the C02 analysis value is useful for enrichment. It may be limited to variations in the direction of application. Therefore, the enrich operation is either an ON-OFF method that turns on the valve when it deviates from the measurement range, or a Higb-L method. A simple W method fil is sufficient.

In the furnace atmosphere control system using this method, a predetermined amount of Co.

It is known that after deviation from the set value and start of enrichment, the response starts in about 1.5 minutes, and becomes almost stable within 3 to 10 minutes.

FIG. 4 shows a schematic diagram of this system. Under the above conditions, sampling, filtering, and analysis can be performed during continuous maintenance between injuries, and the atmosphere can be controlled by feedback of the analysis results, and the metal structure and dimensional changes during this period are almost completely uniform. I got something.

Next, the present invention will be explained in more detail with reference to Examples.

The example furnace is a continuous mesh belt furnace (600 r
tas width belt), the effective furnace length is 4106, and the gas flow rate is as shown in Fig. 5.
10 /H-B te15'''/i4, c-(' 2
0 ``''/H, Z ysum'' switch gas introduces B 0.2 /H in the case where B'''cCO, exceeds the set value, and performs ON-OFF MiIJ control.

Next, set 1130°C as follows (row 5° (al
Sintered body Cfp=0.65-0.75 (COt=0.
1% or less) fbl Sintered body Cchi = 0.4 to o, s (CO, Che 0.2chi to 0.3%) Two cases are set. In this case, the generated gas CO,
The amount should be 0.3 to 0.4 chi.

fa), the upper limit of CO2 gas is set at 0.08 t, and if this is exceeded, enriched gas (C1
(478 section, C, H, 10%) continues to flow and turns off when it reaches 0.08 inch CO.

In the case of fbl, the upper limit of I'1CO2 is set to 0.35%.

With this configuration, the following effects were obtained.

(1) Previously, measurements were made intermittently and corrections were made, but continuous control has become possible.

(2) Equalization of material properties and stabilization of dimensional changes were achieved. For example, Fe(Bat)-1,5*Cu-0,
5t! The conventional dimensional change rate of the JC material 0100111I+ varied due to expansion in the range of 0.14 to 0.2196, but in the present invention, the rate of dimensional change was converged and stabilized in the range of 0.17 to 0.20%. Also, Fe(Bal) -2,0%C
With a composition of u-0.7%C, some cementite precipitation was observed on the outer periphery of a conventional $100 inch monosoke;
However, in the present invention, the structure of the surface layer became stable, and the dimensional change rate was 0.22 to 0.32 compared to the conventional one. blood,
The expansion coefficient was stabilized in the range of 0.25 to 0.30.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an example of a continuous mesh belt type sintering furnace, Fig. 2 is a sectional view of an embodiment of the present invention, and Fig. 3 is a sampling in the sintering section of the embodiment of Fig. 2. rank and R
Diagram showing the relationship between the introduction position IK of x gas and the temperature curve, No. 4
The figure is a furnace atmosphere control diagram in the embodiment of the second L-nu1, and FIG. 5 is a schematic diagram showing numerical reduction of the Rx gas and enrich gas in the embodiment of FIG. 2. Patent Applicant: Sanyume Metal Co., Ltd. Agent Yoshi Shirakawa Itl Figure 3 (Wariku's first Figure 4

Claims (1)

[Claims] (1) A continuous double-densification furnace for FC powder metallurgy, which is equipped with a dewaxing section, a sintering section, and a cooling section, and the in-furnace gas sampling pipe for analysis is
A filter is installed between the central position of the sintering part and a position spaced from the central position in the direction of the length of the furnace by a length equivalent to ten or more of the total length of the sintering part, and a filter is installed in the furnace gas sampling tube 1174.
A carbon potential measuring meter is installed at 110 points, and at least one carbon potential measuring meter is installed at a position spaced apart by a length corresponding to 10 to 20% of the length of the sintered part toward the rear of the furnace from the installation position of the in-furnace gas sampling pipe. Connect the inlet pipe for endothermic shift reactor air as a protective atmosphere, and open the enriched gas charging pipe at a position 1 m or more away from the open end of the shift reactor air inlet pipe to collect the in-furnace gas. and a continuous sintering furnace configured to maintain the carbon potential of the gas in the furnace at a predetermined value by controlling the amount of enriched gas charged through analysis.